update github workflow since github includes firefox & snaps in the default runner image, which causes the build to fail.

going to need a custom runner I guess...might as well only do actions on gitea.

.github/workflows/daily.yaml

@@ -3,7 +3,7 @@ on:
   push:
     branches: [ $default-branch ]
   schedule:
-    - cron: "0 7 * * *"   # daily 07:00
+    - cron: "0 7 * * 1"   # mondays at 07:00
   workflow_dispatch: {}
 
 jobs:

.gitignore

@@ -9,3 +9,5 @@ stevia-log
 .vscode/
 *.map
 compose-dev.yaml
+eth_null-tx.log
+eth_null-txdump.txt

README.md

@@ -1,6 +1,6 @@
 # Stevia Bootloader
 
-Stevia is a lightweight, hobby bootloader written in Assembly and C, designed for educational purposes. It targets x86 (Pentium III era) and aims to be simple, approachable, and understandable, focusing on minimalism and core functionality.
+Stevia is a lightweight, hobby bootloader written in Assembly and C, designed for educational purposes. It targets 686+ and aims to be simple, approachable, and understandable, focusing on minimalism and core functionality.
 
 ## Features
 
@@ -10,18 +10,13 @@ Stevia is a lightweight, hobby bootloader written in Assembly and C, designed fo
 - **Stage 2 Bootloader**: Loads the kernel into memory and passes control.
 - **Basic Filesystem Support**: Initial filesystem recognition (details depend on implemented filesystem support).
 - **Memory Map Parsing**: Detects available memory regions via BIOS interrupts.
-- **GDT Initialization**: Sets up the Global Descriptor Table for protected mode.
+- **GDT Initialization**: Sets up the Global Descriptor Table for protected/unreal mode.
-
-### In Progress
-
-- **Interrupt Descriptor Table (IDT) Setup**: Setting up basic interrupt handling.
-- **Basic Keyboard Input**: Initial support for capturing keystrokes.
 
 ### Planned Features
 
-- **Task Scheduling**: Basic round-robin task switching.
+- **Interrupt Descriptor Table (IDT) Setup**: Setting up basic interrupt handling.
+- **Basic Keyboard Input**: Initial support for capturing keystrokes.
 - **Filesystem Expansion**: Support for additional filesystems.
-- **More Robust Driver Support**: Additional hardware drivers, such as for storage devices.
 
 ## Installation
 
@@ -29,41 +24,37 @@ Stevia is a lightweight, hobby bootloader written in Assembly and C, designed fo
 
 To build and run Stevia, you will need the following tools installed on your system:
 
-- **Assembler**: NASM for assembling bootloader components.
+- **Assembler**: NASM for assembling bootloader components, you could use a compatible assembler but YMMV.
-- **C Compiler**: GCC (cross-compiler recommended).
+- **GNU make**: For building the project.
-- **Emulator**: Bochs or QEMU for testing.
+- **mtools**: To access the FAT partition
-- **GNU Make**: For building the project.
+- **fdisk**: To create disk images and setup partition tables
-- **Utilities**:
+- **dosfstools**: FAT32 creation
-  - **dd**: For creating raw disk images.
+- **an x86 Emulator**: Bochs is the primary dev target, but stevia should run on any x86 emulator/hardware with at least a Pentium 3 and 640KiB of memory.
-  - **losetup** (Linux only): For associating loop devices with disk images.
-  - **sfdisk**: For creating DOS disk partitions.
-  - **mkfs.fat**: For formatting partitions as FAT32.
-  - **hdiutil** (macOS only): For attaching disk images.
-  - **newfs\_msdos** (macOS only): For formatting FAT32 partitions.
 
 ### Building and Running
 
 1. **Clone the repository**:
+
    ```sh
    git clone https://github.com/Nivirx/stevia.git
    cd stevia
    ```
+
 2. **Build the bootloader and create a bootable disk image**:
+
    ```sh
-   sudo make
+   make
    ```
+
 3. **Run using Bochs**:
+
    ```sh
-   bochs -f bochsrc.txt
+   bochs -q -f bochsrc.txt
    ```
 
 ## Project Goals
 
-Stevia is intended to be a learning tool for those interested in low-level programming, focusing on understanding the basics of how a computer starts up and manages early system resources. Contributions and forks are welcome, especially from those interested in expanding the functionality.
+Stevia is intended to be a learning tool for those interested in low-level programming, focusing on understanding the basics of how a computer starts up and manages early system resources.
-
-## Contributing
-
-We welcome contributions! Feel free to open issues for bugs or feature requests, and submit pull requests for any improvements. Please ensure that your code follows the existing style and includes appropriate comments.
 
 ## License
 

bochsrc.txt

@@ -1,44 +1,44 @@
-# configuration file generated by Bochs
+#
-plugin_ctrl: voodoo=false, unmapped=true, biosdev=true, speaker=true, extfpuirq=true, parallel=true, serial=true, busmouse=false, e1000=false, es1370=false, gameport=true, ne2k=false, sb16=false, usb_uhci=false, usb_ohci=false, usb_ehci=false, usb_xhci=false
+# Bochs config
+#
 config_interface: textconfig
 display_library: x, options=gui_debug
-memory: guest=64, host=64, block_size=128
+plugin_ctrl: voodoo=false, unmapped=true, biosdev=true, speaker=true, extfpuirq=true, parallel=true, serial=true, busmouse=false, e1000=true, es1370=false, gameport=true, ne2k=false, sb16=false, usb_uhci=true, usb_ohci=false, usb_ehci=false, usb_xhci=false
-romimage: file="/usr/share/bochs/BIOS-bochs-legacy", address=0x00000000, options=none, flash_data=none
+print_timestamps: enabled=1
-vgaromimage: file="/usr/share/bochs/VGABIOS-lgpl-latest"
-boot: disk
-floppy_bootsig_check: disabled=0
-floppya: type=1_44
-# no floppyb
-ata0: enabled=true, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
-ata0-master: type=disk, path="./build/disk.img", mode=flat, cylinders=0, heads=0, spt=0, sect_size=512, model="Stevia Disk", biosdetect=auto, translation=lba
-ata0-slave: type=none
-ata1: enabled=false
-ata1-master: type=none
-ata1-slave: type=none
-ata2: enabled=false
-ata3: enabled=false
-optromimage1: file=none
-optromimage2: file=none
-optromimage3: file=none
-optromimage4: file=none
-optramimage1: file=none
-optramimage2: file=none
-optramimage3: file=none
-optramimage4: file=none
-pci: enabled=1, chipset=i440fx, slot1=none, slot2=none, slot3=none, slot4=none, slot5=none
-vga: extension=vbe, update_freq=10, realtime=1, ddc=builtin
-cpu: count=1, ips=1000000, model=p3_katmai, reset_on_triple_fault=1, cpuid_limit_winnt=0, ignore_bad_msrs=1, mwait_is_nop=0
-print_timestamps: enabled=0
-port_e9_hack: enabled=false, all_rings=false
 private_colormap: enabled=0
-clock: sync=none, time0=local, rtc_sync=0
-# no cmosimage
 log: -
 logprefix: %t%e%d
 debug: action=ignore
 info: action=report
 error: action=report
 panic: action=ask
+magic_break: enabled=1
+port_e9_hack: enabled=1, all_rings=false
+#
+# Machine Spec
+# 1x Pentium 3 @ (1M IPS) w/ 64MiB of System memory on the i440fx
+cpu: count=1, ips=1000000, model=p3_katmai, reset_on_triple_fault=0, cpuid_limit_winnt=0, ignore_bad_msrs=1, mwait_is_nop=0
+memory: guest=64, host=64, block_size=128
+romimage: file="/usr/share/bochs/BIOS-bochs-legacy", address=0x00000000, options=none, flash_data=none
+vgaromimage: file="/usr/share/vgabios/vgabios-stdvga.bin"
+pci: enabled=1, chipset=i440fx
+vga: extension=vbe, update_freq=10, realtime=1, ddc=builtin
+clock: sync=none, time0=local, rtc_sync=0
+#
+# Disks
+#
+boot: disk
+floppy_bootsig_check: disabled=0
+floppya: type=1_44
+floppyb: type=1_44
+ata0: enabled=true, ioaddr1=0x1f0, ioaddr2=0x3f0, irq=14
+ata0-master: type=disk, path="./build/disk.img", mode=flat, cylinders=0, heads=0, spt=0, sect_size=512, model="Stevia Disk", biosdetect=auto, translation=lba
+ata0-slave: type=none
+#
+# Other hardware
+#
+usb_ehci: enabled=1, companion=ohci
+e1000: enabled=1, mac=52:54:00:12:34:56, ethmod=null
 keyboard: type=mf, serial_delay=150, paste_delay=100000, user_shortcut=none
 mouse: type=none, enabled=false, toggle=ctrl+mbutton
 sound: waveoutdrv=dummy, waveout=none, waveindrv=dummy, wavein=none, midioutdrv=dummy, midiout=none
@@ -48,6 +48,4 @@ parport2: enabled=false
 com1: enabled=true, mode=null
 com2: enabled=false
 com3: enabled=false
-com4: enabled=false
+com4: enabled=false
-magic_break: enabled=1
-port_e9_hack: enabled=1, all_rings=false

include/BIOS/func/E820_memory_map.nasm

@@ -35,7 +35,7 @@ endstruc
 
 ALIGN 4, db 0x90
 GetMemoryMap:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
     push es         ; save segment register
 .func:
     mov dword [SteviaInfo + SteviaInfoStruct_t.MemoryMapEntries], 0
@@ -53,6 +53,7 @@ GetMemoryMap:
 .loop_L1:
     mov eax, 0x0000E820                     ; select 0xE820 function
     mov edx, 0x534D4150                     ; 'SMAP' magic
+    clc                                     ; clear carry
     int 0x15
     jc GetMemoryMap.error
     cmp eax, 0x534D4150
@@ -82,11 +83,11 @@ GetMemoryMap:
     ERROR STAGE2_MM_E820_NO_SMAP
 .endp:
     pop es
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 PrintMemoryMap:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
     mov eax, dword [SteviaInfo + SteviaInfoStruct_t.MemoryMapEntries]
     cmp eax, 0
@@ -105,15 +106,15 @@ PrintMemoryMap:
     ; print_string strformat_buffer
     
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 FormatMemoryMapEntry:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
     ; create a string buffer somewhere and return address to result string in ax
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 

include/BIOS/func/a20enable.nasm

@@ -64,7 +64,7 @@
 ;    Bits 6-7 - 00: HDD activity LED off; any other value is "on"
 ALIGN 4, db 0x90
 EnableA20:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
     push ds
     push es
 .a20_check:
@@ -105,6 +105,7 @@ EnableA20:
     je EnableA20.endp         ; A20 is already enabled
 
     mov ax, 0x2403
+    clc                             ; clear carry
     int 0x15
     jc EnableA20.do_fallback_a20    ; carry = error...not supported?
     cmp ah, 0
@@ -121,6 +122,7 @@ EnableA20:
     ERROR STAGE2_A20_FAILED
 .do_bios_a20:
     mov ax, 0x2401
+    clc                             ; clear carry
     int 0x15
     jmp EnableA20.a20_check
 .do_fast_a20:
@@ -132,7 +134,7 @@ EnableA20:
 .endp:
     pop es
     pop ds
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
     
 %endif

include/BIOS/func/ext_read.nasm

@@ -76,7 +76,7 @@ endstruc
 ;                         uint16_t count, uint8_t drive_num)
 ALIGN 4, db 0x90
 read_disk_raw:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:                        
     mov ax, LBAPkt_t_size
     push ax                 ; len
@@ -111,6 +111,7 @@ read_disk_raw:
     mov ah, 0x42                ; call #
     mov dl, byte [bp + 14]      ; drive #             
 
+    clc                         ; clear carry
     int 0x13
     jnc .endf
 
@@ -122,7 +123,7 @@ read_disk_raw:
     ERROR STAGE2_MBR_DISK_READ_ERROR
     %endif
 .endf:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 %endif

include/BIOS/func/video.nasm

@@ -20,25 +20,27 @@
 ALIGN 4, db 0x90
 SetTextMode:
 .prolog:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
     pushf
 .func:
     xor ah, ah                  ; Set Video mode BIOS function
-    mov al, 0x02                ; 16 color 80x25 Text mode
+    mov al, 0x03                ; 16 color 80x25 Text mode
     int 0x10                    ; Call video interrupt
+                                
 
     mov ah, 0x05                ; Select active display page BIOS function
     xor al, al                  ; page 0
     int 0x10                    ; call video interrupt
 .endp:
     popf
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
-; disables blinking text mode cursor
+; disables blinking text mode cursor via crtc pokes
+; 0x3D4/0x3D5 for color, mono at 0x3B4/0x3B5
 ALIGN 4, db 0x90
-disable_cursor:
+disable_cursor_crtc:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
     mov dx, 0x3D4
 	mov al, 0xA	    ; low cursor shape register
@@ -48,8 +50,126 @@ disable_cursor:
 	mov al, 0x20	; bits 6-7 unused, bit 5 disables the cursor, bits 0-4 control the cursor shape
 	out dx, al
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
+    ret
+
+; disables blinking text mode cursor via BIOS int 10h, ah = 01
+ALIGN 4, db 0x90
+disable_cursor_bios:
+    __CDECL16_PROC_ENTRY
+.func:
+    push bx
+    mov  ah, 03h      ; read cursor pos & shape
+    xor  bh, bh
+    int  10h          ; CH=top scanline, CL=bottom
+
+    or   ch, 20h      ; set bit 5 = disable
+    mov  ah, 01h      ; set leaf 01h
+    int  10h
+    pop  bx
+.endp:
+    __CDECL16_PROC_EXIT
+    ret
+
+; Prints a C-Style string (null terminated) using BIOS vga teletype call
+; void PrintString(char* buf)
+ALIGN 4, db 0x90
+PrintString:
+    __CDECL16_PROC_ENTRY
+    mov di, [bp + 4]    ; first arg is char[] 
+.str_len:
+    xor cx, cx         ; ECX = 0
+    not cx             ; ECX = -1 == 0xFFFF
+    xor ax, ax         ; search for al = 0x0
+
+    cld
+    repne scasb        ; deincrement cx while searching for al
+
+    not cx             ; the inverse of a neg number = abs(x) - 1
+    dec cx             ; CX contains the length of the string - nul byte at end
+.print:
+    mov si, [bp + 4]            ; source string
+.print_L0:
+    movzx ax, byte [si]
+    %ifdef __STEVIA_DEV_DEBUG
+    out 0xe9, byte al           ; bochs magic debug port
+    %endif
+    push ax
+    call PrintCharacter
+    add sp, 0x2
+
+    inc si
+    dec cx
+
+    jcxz PrintString.endp
+    jmp PrintString.print_L0    ; Fetch next character from string
+.endp:
+    __CDECL16_PROC_EXIT
+    ret                         ; Return from procedure
+
+; Prints a single character
+; void PrintCharacter(char c);
+ALIGN 4, db 0x90
+PrintCharacter:
+    __CDECL16_PROC_ENTRY
+.func:
+    mov al, byte [bp + 4]       ; AL = character c
+    mov ah, 0x0E                ; INT 0x10, AH=0x0E call
+    mov bx, 0x0007              ; BH = page no. BL =Text attribute
+    int 0x10                    ; call video interrupt
+                                ; TODO: check for carry and clear carry before call
+.endp:
+    __CDECL16_PROC_EXIT
+    ret
+
+; TODO: fix the prolog, epilog and stack usage to confirm with cdecl16
+; prints the hex representation of of val
+; void PrintDWORD(uint32_t val);
+ALIGN 4, db 0x90
+PrintDWORD:
+    __CDECL16_PROC_ENTRY
+.func: 
+    mov si, IntToHex_table
+    mov ebx, 16     ; base-16
+
+    mov eax, dword [bp + 4]     ;val
+
+    xor edx, edx
+    xor cx, cx
+.next_digit:
+    div ebx            ; dividend in edx:eax -> quotient in eax, remainder in edx
+    push dx            ; save remainder
+    inc cx
+
+    xor dx, dx
+    test eax, eax
+    jnz PrintDWORD.next_digit
+
+.zero_pad:
+    cmp cx, 0x0008
+    je PrintDWORD.print_stack
+    xor ax, ax
+    push ax
+    inc cx
+    jmp PrintDWORD.zero_pad
+
+.print_stack:
+    pop bx
+    dec cx
+    push cx
+
+    movzx ax, byte [bx+si+0]    ; bx = index into Hex lookup table
+    push ax
+    call PrintCharacter
+    add sp, 0x2
+
+    pop cx
+
+    jcxz PrintDWORD.endp
+    jmp PrintDWORD.print_stack
+
+.endp:
+    __CDECL16_PROC_EXIT
     ret
-    
 %endif
 %define __INC_VIDEO

include/cdecl16.inc

@@ -13,20 +13,23 @@
 ;     You should have received a copy of the GNU General Public License
 ;     along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
-%ifnmacro __CDECL16_ENTRY
+%ifnmacro __CDECL16_PROC_ENTRY
-%macro __CDECL16_ENTRY 0
+%macro __CDECL16_PROC_ENTRY 0-1
     push bp
     mov bp, sp
-    sub sp, 0x10
 
     push si
     push di
     push bx
+
+    %if %0 = 1
+    sub  sp, %1        ; reserve locals only when needed
+    %endif
 %endmacro
 %endif
 
-%ifnmacro __CDECL16_EXIT
+%ifnmacro __CDECL16_PROC_EXIT
-%macro __CDECL16_EXIT 0
+%macro __CDECL16_PROC_EXIT 0
     pop bx
     pop di
     pop si
@@ -36,19 +39,88 @@
 %endmacro
 %endif
 
-%ifnmacro __CDECL16_CALLER_SAVE
+; __CDECL16_PROC_ARGS nargs
-%macro __CDECL16_CALLER_SAVE 0
+;   Creates %$arg1 .. %$argN as [bp+4], [bp+6], ...
-    push ax
+;   for use inside of function bodies
-    push cx
+%ifnmacro __CDECL16_PROC_ARGS
-    push dx
+%macro __CDECL16_PROC_ARGS 1
+    %push __CDECL16_PROC_ARGS
+    %assign %$__i 1
+    %rep %1
+        %xdefine %$arg%$__i  [bp + 4 + 2*(%$__i-1)]
+        %assign  %$__i %$__i + 1
+    %endrep
+    %pop
 %endmacro
 %endif
 
-%ifnmacro __CDECL16_CALLER_RESTORE
+; __CDECL16_CALL_ARGS a,b,c  ==> push c / push b / push a
-%macro __CDECL16_CALLER_RESTORE 0
+;   handles pushing values to the stack in the correct order
-    pop dx
+%ifnmacro __CDECL16_CALL_ARGS
-    pop cx
+%macro __CDECL16_CALL_ARGS 1-*
-    pop ax
+    %rep %0
+        %rotate -1      ; move the last argument into %1
+        push %1         ; push last, then next-to-last, ...
+    %endrep
+%endmacro
+%endif
+
+; __CDECL16_CALL func, nargs   ; adds sp by nargs*2 after call
+;   adds up word pushes to restore stack frame
+;   WARNING: if you push a dword it will only count 2, use __CDECL16_CALL_ARGS_SIZED
+%ifnmacro __CDECL16_CALL
+%macro __CDECL16_CALL 2
+    call %1
+    add  sp, %2*2
+%endmacro
+%endif
+
+; __CDECL16_CALL_ARGS_SIZED func, size1[, size2 ...]  ; sizes in BYTES
+;   if you *need* to pass dword sized args in 16-bit mode, use this to properly
+;   count the stack frame to restore later!
+%ifnmacro __CDECL16_CALL_ARGS_SIZED
+%macro __CDECL16_CALL_ARGS_SIZED 2-*
+    %push __CDECL16_CALL_ARGS_SIZED
+    call %1
+    %assign %$__sum 0
+    %assign %$__i 2
+    %rep %0-1
+        %assign %$__sum %$__sum + %[%$__i]   ; sizes may be expressions
+        %assign %$__i %$__i + 1
+    %endrep
+    %if %$__sum & 1
+        %error "__CDECL16_CALL_ARGS_SIZED: total size is odd; pushes must sum to whole bytes actually pushed (usually even)."
+    %endif
+    add sp, %$__sum
+    %pop
+%endmacro
+%endif
+
+%ifnmacro __CDECL16_CLOB
+; Save registers in the order listed. Supports "flags" as a pseudo-reg.
+%macro __CDECL16_CLOB 1-*
+    %rep %0
+        %ifidni %1, flags
+            pushf
+        %else
+            push %1
+        %endif
+        %rotate 1
+    %endrep
+%endmacro
+%endif
+
+%ifnmacro __CDECL16_UNCLOB
+; Restore in reverse order of CLOB. Supports "flags".
+%macro __CDECL16_UNCLOB 1-*
+    %rep %0
+        %rotate -1
+        %ifidni %1, flags
+            popf
+        %else
+            pop %1
+        %endif
+    %endrep
 %endmacro
 %endif
 

include/fat32/FAT32_SYS.inc

@@ -23,16 +23,11 @@
 ; returns: none
 ALIGN 4, db 0x90
 InitFATDriver:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
-    mov ax, FAT32_State_t_size
+
-    push ax                     ; length of fat32_state structure
+    __CDECL16_CALL_ARGS fat32_state, 0x0000, FAT32_State_t_size
-    xor ax, ax
+    __CDECL16_CALL kmemset, 3
-    push ax                     ; init fat32_state with zero
-    mov ax, fat32_state
-    push ax                     ; address of structure
-    call kmemset
-    add sp, 0x6
 
 .calc_active_part:
     mov ax, word [partition_offset]            
@@ -70,14 +65,14 @@ InitFATDriver:
     mov eax, dword [bx + FAT32_ebpb_t.root_clus_dword]
     mov dword [di + FAT32_State_t.curr_dir_cluster_32], eax
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 .error:
     ERROR STAGE2_FAT32_INIT_CF
 
 ALIGN 4, db 0x90
 FSInfoPrinter:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
     ;info we want to print to validate we are loading stuff from the disk correctly
     ; boot_drive # (i.e 0x80)
@@ -88,7 +83,7 @@ FSInfoPrinter:
     ; print entire FAT32 state
     ;
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 .error:
     ERROR STAGE2_ERROR_INFOPRINTER
@@ -104,18 +99,19 @@ FSInfoPrinter:
 ; uint32_t SearchFATDIR(uint8_t* SFN);
 ALIGN 4, db 0x90
 SearchFATDIR:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .file_lookup:
-    print_string SearchFATDIR_info
+    __CDECL16_CALL_ARGS SearchFATDIR_info
+    __CDECL16_CALL PrintString, 1
+
     mov bx, fat32_state
     .load_first_dir:
-        mov eax, dword [bx + FAT32_State_t.curr_dir_cluster_32]
+
-        push dword eax          ; cluster
+        ; uint8_t ReadFATCluster(uint16_t seg, uint16_t offset, uint32_t cluster)
-        mov ax, dir_buffer
+        push dword [bx + FAT32_State_t.curr_dir_cluster_32]          ; cluster
-        push ax                 ; offset
+        push dir_buffer                                              ; offset
-        xor ax, ax
+        push 0x0000                                                  ; segment
-        push ax                 ; segment
+        call ReadFATCluster
-        call ReadFATCluster     ; uint8_t ReadFATCluster(uint16_t seg, uint16_t offset, uint32_t cluster)
         add sp, 0x8
 
         mov si, dir_buffer
@@ -124,10 +120,10 @@ SearchFATDIR:
     .load_next_dir:
         ; if eax >= 0x0FFFFFF8 then there are no more clusters (end of chain)
         ; if eax == 0x0FFFFFF7 then this is a cluster that is marked as bad
-        
+
-        mov eax, dword [bx + FAT32_State_t.curr_dir_cluster_32]
+        ; uint32_t NextCluster(uint32_t active_cluster);
-        push dword eax
+        push dword [bx + FAT32_State_t.curr_dir_cluster_32]
-        call NextCluster        ; uint32_t NextCluster(uint32_t active_cluster);
+        call NextCluster        
         add sp, 0x4
 
         cmp eax, 0x0fff_fff7
@@ -137,16 +133,14 @@ SearchFATDIR:
 
     .load_next_dir_next_OK:
         ; load 512 bytes of directory entries from data sector
-        mov eax, [bx + FAT32_State_t.curr_dir_cluster_32]
-        push dword eax          ; cluster
 
-        mov ax, dir_buffer    
+        ; uint8_t ReadFATCluster(uint16_t seg, uint16_t offset, uint32_t cluster)
-        push ax                 ; offset
+        push dword [bx + FAT32_State_t.curr_dir_cluster_32] ; cluster   
+        push dir_buffer                                     ; offset
+        push 0x0000                                         ; segment
+        call ReadFATCluster     
+        add sp, 0x8
 
-        xor ax, ax
-        push ax                 ; segment
-        call ReadFATCluster     ; uint8_t ReadFATCluster(uint16_t seg, uint16_t offset, uint32_t cluster)
-        sub sp, 0x8
     .empty_dir_entry:
         ; check for 0x0 in first byte, if true then there are no more files
         ; if true we did not find the file, we should error here
@@ -176,7 +170,9 @@ SearchFATDIR:
 
     ; TODO: move this to a seperate string search function
     .parse_dir:
-        print_string MaybeFound_Boot_info
+        __CDECL16_CALL_ARGS MaybeFound_Boot_info
+        __CDECL16_CALL PrintString, 1
+        
         .lfn_check:
             ; check for ATTR_READ_ONLY | ATTR_HIDDEN | ATTR_SYSTEM | ATTR_VOLUME_ID  (0x0F) in offset 11
             ; TODO: going to skip LFN for now, since all valid volumes will have SFN's
@@ -201,7 +197,7 @@ SearchFATDIR:
             mov ax, [si + FAT32_SFN_t.cluster_16_low]
             ; eax == first cluster of file
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 ; BUG: this function needs review
@@ -210,20 +206,15 @@ SearchFATDIR:
 ; if eax == 0x0FFFFFF7 then this is a cluster that is marked as bad
 ALIGN 4, db 0x90
 NextCluster:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
-    print_string NextFATCluster_info
+    __CDECL16_CALL_ARGS NextFATCluster_info
+    __CDECL16_CALL PrintString, 1
 
-    mov ax, FAT32_NextClusterData_t_size
+    __CDECL16_CALL_ARGS fat32_nc_data, 0x0000, FAT32_NextClusterData_t_size
-    push ax                     ; length
+    __CDECL16_CALL kmemset, 3
-    xor ax, ax
-    push ax                     ; init with zero
-    mov ax, fat32_nc_data
-    push ax                     ; address of structure
-    call kmemset
-    add sp, 0x6
 
-    mov edx, dword [bp + 4]
+    mov edx, dword [bp + 4]                      ; active_cluster
     mov si, fat32_nc_data                        ; instead of push/pop and moving the data back
     mov di, fat32_bpb                            ; load si & di then use xchg
     mov bx, fat32_state
@@ -270,12 +261,13 @@ NextCluster:
 ;                         uint32_t lba,
 ;                         uint16_t count, uint16_t drive_num)
 .read_cluster:
-; next_cluster = fat_buffer[entry_offset]
+    ; next_cluster = fat_buffer[entry_offset]
     mov ebx, dword [si + FAT32_NextClusterData_t.entry_offset]
     mov si, fat_buffer
     mov eax, dword [bx+si+0]
+    ; BUG: ???
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 .error_cfdivz:
     ERROR STAGE2_FAT32_NCLUS_CFDIVZ
@@ -283,9 +275,10 @@ NextCluster:
 ; uint8_t ReadFATCluster(uint16_t seg, uint16_t offset, uint32_t cluster)
 ALIGN 4, db 0x90
 ReadFATCluster:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
-    print_string ReadFATCluster_info
+    __CDECL16_CALL_ARGS ReadFATCluster_info
+    __CDECL16_CALL PrintString, 1
 
     mov bx, fat32_bpb
     mov si, fat32_ebpb
@@ -318,7 +311,7 @@ ReadFATCluster:
     call read_disk_raw  
     add sp, 0xC
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 .error:
     ERROR STAGE2_FAT32_CLS2LBA_CF

include/util/arena_alloc.nasm

@@ -12,18 +12,19 @@ endstruc
 ; void arena_init(ArenaState *a)
 ;
 arena_init:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
-    movzx eax, word [bp + 4]     ; ptr to state structure
+    mov ax, word [bp + 4]     ; ptr to state structure
     mov di, ax
 
-    xor eax, eax
+    xor ax, ax
-    mov word [di + ArenaStateStruc_t.mark], eax
+    mov word [di + ArenaStateStruc_t.mark], ax
     mov word [di + ArenaStateStruc_t.end], word (__ARENA_HEAP_START + __ARENA_HEAP_SIZE)
     mov word [di + ArenaStateStruc_t.start], __ARENA_HEAP_START
 
     ; zero out heap area on init
     ; void* kmemset_byte(void* dst, uint8_t val, uint16_t len);
+    ; TODO: use word or qword spacing at least to speed this up
     mov ax, __ARENA_HEAP_SIZE
     push ax                     ; len
     xor ax, ax
@@ -34,50 +35,134 @@ arena_init:
     add sp, 0x6
 
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 ; size_t align_up(size_t x, size_t a)
+; ax, bx. cx are all clobbered
+; align x up to the nearest specified alignment (a), a should be a power of 2
+; (x + (a-1)) & ~(a-1)
+; return value in ax
 arena_align_up:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
-    ; align the mark to the nearest specified alignment
+    ; if a == 0 return x
+    mov ax, [bp + 4]      ; x
+    mov bx, [bp + 6]      ; a
+
+    test bx, bx
+    jz .endp              
+
+    ; enforce power-of-two for alignment, return x
+    ; for example...
+    ; alignment = 0x0010,
+    ;    0x0010 & (0x0010 - 0x0001)
+    ;    0x0010 & 0x000F -> 1_0000000b & 0_11111111b => 0b == zero
+    ;
+    ; alignment = 0x0006
+    ;    0x0006 & (0x0006 - 0x0001)
+    ;    0x0006 & 0x0005 -> 00000110b & 00000101b => 00000100b != 0
+    ;
+    ; i.e any power of 2 has only 1 bit set in binary (2 = 0010b, 4 = 0100b, 8 = 1000b and so on)
+    ;  subtracting 1 from a power of 2 'flips' lower bits ( 7 = 0111b, 15 = 1111b ...) 
+    ;  so 'and'ing a power of two with (itself - 1) will result in none of the bit's being set
+    mov cx, bx
+    dec cx
+    test bx, cx
+    jnz .endp
+
+    dec bx                ; a - 1
+
+    mov cx, ax
+    add cx, bx            ; x + (a-1)
+    not bx                ; ~(a-1)
+
+    and cx, bx            ; and with the inverse
+
+    mov ax, cx            ; move to ax and return
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
-; void* arena_alloc(void* a, size_t bytes, size_t align)
+; void* arena_alloc(size_t bytes, size_t align)
+; bp-2 - current used arena (i.e 'highmark')
+; bp-4 - aligned_ptr 
+; bp-6 - new_end
 arena_alloc:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY 0x10
 .func:
     ; remove bytes from pool and increment mark to the new cursor location
     ; return a pointer to the begining of  allocated segment
+    mov bx, early_heap_state
+    
+    mov ax, word [bx + ArenaStateStruc_t.start]
+    mov dx, word [bx + ArenaStateStruc_t.mark]
+    add ax, dx                      ; i.e the total used arena
+    mov word [bp - 2], ax           ; save as a local
+
+    push bx                         ; save heap_state pointer
+
+    mov ax, word [bp + 6]           ; requested next allocation alignment
+    push ax
+    mov ax, word [bp - 2]           ; current arena 'highmark'
+    push ax
+    call arena_align_up
+    add sp, 0x4
+    mov word [bp - 4], ax           ; save return value
+
+    pop bx                          ; restore heap_state pointer
+
+    ; new_end = aligned_ptr + bytes 
+    add ax, word [bp + 4]           ; add to total (so current aligned mark + bytes)
+    mov word [bp - 6], ax           ; save as local
+
+    mov dx, word [bx + ArenaStateStruc_t.end]
+    cmp ax, dx
+    ja arena_alloc.error            ; if our heap end is < the requested throw an error, heap is full
+                                    ; else update the mark to the new value & return  the aligned pointer
+
+    ; mark_delta = new_end - curr_used
+    mov dx, word [bp - 6]
+    sub dx, word [bp - 2]
+
+    ; mark += mark_delta
+    mov ax, word [bx + ArenaStateStruc_t.mark]
+    add ax, dx
+    mov word [bx + ArenaStateStruc_t.mark], ax
+    
+    ; return aligned_ptr
+    mov ax, word [bp - 4]
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
+.error:
+    ERROR STEVIA_DEBUG_ERR
 
 arena_mark:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
     ; return the current location of the 'cursor' in the allocator
+    ERROR STEVIA_DEBUG_UNIMPLEMENTED
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 arena_reset_to:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
     ; rewind the arena to a previously marked point
+    ERROR STEVIA_DEBUG_UNIMPLEMENTED
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 arena_reset:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
     ; reset the entire heap to a fresh state
+    ERROR STEVIA_DEBUG_UNIMPLEMENTED
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 %endif

include/util/kmem_func.nasm

@@ -19,7 +19,7 @@
 ; void* kmemset_byte(void* dst, uint8_t val, uint16_t len);
 ALIGN 4, db 0x90
 kmemset:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
  .func:
     mov     cx, [bp + 8]        ; uint16_t len
     mov     al, byte [bp + 6]   ; uint8_t val
@@ -29,14 +29,14 @@ kmemset:
     rep     stosb
     mov     ax, di         ; return pointer to dest + len (last elem of dest)
 .endp:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 ; uint8_t* kmemset(uint16_t* dest, uint16_t* src, uint16_t len);
 ; not overlap safe
 ALIGN 4, db 0x90
 kmemcpy:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .func:
     mov cx, [bp + 8]        ; len
     mov si, [bp + 6]        ; src
@@ -46,7 +46,7 @@ kmemcpy:
     rep movsb
     mov ax, di              ; return pointer to dest
 .endf:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 %endif

include/util/kmemcpy5_func.nasm

@@ -20,7 +20,7 @@
 ; not overlap safe, only for
 ALIGN 4, db 0x90
 kmemcpy5:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
     push ds
     push es
 .setup_segments:
@@ -41,7 +41,7 @@ kmemcpy5:
     pop es
     pop ds
 .endf:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 %define __INC_KMEMCPY5_FUNC

include/util/kmemset4_func.nasm

@@ -19,7 +19,7 @@
 ; word kmemset_byte(word segment, word dst, byte val, word len);
 ALIGN 4, db 0x90
 kmemset4:
-    __CDECL16_ENTRY
+    __CDECL16_PROC_ENTRY
 .setup_segment:
     push es
     mov ax, [bp + 4]
@@ -35,7 +35,7 @@ kmemset4:
 .restore_segments:
     pop es
 .endf:
-    __CDECL16_EXIT
+    __CDECL16_PROC_EXIT
     ret
 
 %endif

scripts/create-disk.sh

@@ -17,8 +17,7 @@ set -euo pipefail
 #     along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 if [ $(id -u) = 0 ]; then
-   echo "Script should not be run as root, it could break something! Exiting!" >&2
+   echo "Script should not be run as root, it could break something!" >&2
-   exit 1
 fi
 
 # paths to bootcode
@@ -125,8 +124,11 @@ if [[ "$OSTYPE" == "linux-gnu"* ]]; then
         echo "[2/7] Write DOS partition table (single FAT32 LBA @ 2048)"
         "$SF" --no-reread "$disk_img" < /tmp/pt.sfdisk
 
-        echo "[3/7] Make FAT32 filesystem in partition image"
+        # BUG: the default disk img is 256MiB which mkfs.fat wants to create
-        "$MKFS" -v -F32 -s 1 -n 'STEVIAFS' "$part_img"
+        #      a FAT16 FS by default. it needs to be at least 2GiB to to 'lock out'
+        #      FAT16 as an option. Force FAT32 here, might(?) break some things.
+        echo "[3/7] Make FAT filesystem in partition image"
+        "$MKFS" -F32 -v -n 'STEVIAFS' "$part_img"
 
         echo "[4/7] Patch VBR inside partition image (preserve BPB)"
 

src/mbr/mbr.nasm

@@ -58,7 +58,7 @@ init:
     cld
     rep stosb                         ; zero bss section
 
-    sub sp, 0x20                    ; local varible space
+    sub sp, 0x20                    ; local varible space (32 bytes)
     push bp                         ; setup top of stack frame
 
     xor cx, cx
@@ -96,6 +96,8 @@ main:
         mov ah, 0x41
         mov bx, 0x55AA
         mov dl, 0x80
+
+        clc
         int 0x13
         jnc main.find_active
         ERROR MBR_ERROR_NO_INT32E                         ; no extended function support

src/stage2/stage2.nasm

@@ -15,7 +15,7 @@
 
 [BITS 16]
 [ORG 0x0500]                            ; IF YOU CHANGE ORG CHANGE THE SIGN OFFSET AT THE END
-[CPU KATMAI]
+[CPU 686]
 [map all build/stage2.map]
 [WARNING -reloc-abs-byte]
 [WARNING -reloc-abs-word]
@@ -34,13 +34,6 @@
 %include "early_mem.inc"
 %include "error_codes.inc"
 
-%macro print_string 1
-    mov ax, %1
-    push ax
-    call PrintString
-    add sp, 0x2
-%endmacro
-
 section .text
 begin_text:
 ; dl = byte boot_drive
@@ -88,7 +81,7 @@ init:
     jmp word __STAGE2_SEGMENT:main
 
 ; ###############
-; Functions
+; Core Functions
 ; ###############
 
 %include "util/kmem_func.nasm"
@@ -96,6 +89,11 @@ init:
 %include "util/kmemset4_func.nasm"
 %include "util/error_func.nasm"
 
+; ###############
+; Functions
+; ###############
+%include "util/arena_alloc.nasm"
+
 ; ###############
 ; FAT32 Driver
 ; ###############
@@ -130,51 +128,54 @@ main:
     je main.stage2_main
     ERROR STAGE2_SIGNATURE_MISSING
 .stage2_main:
-    mov ax, PartTable_t_size
+    ; copy partition table data to .data section in stage2
-    push ax                                                 ; len = PartTable_t_size
+    __CDECL16_CALL_ARGS partition_table, word [vbr_part_table_ptr], PartTable_t_size
-    mov ax, word [vbr_part_table_ptr]                       ; src = ptr to vbr partition_table
+    __CDECL16_CALL kmemcpy, 3
-    push ax
-    mov ax, partition_table                                 ; dst
-    push ax
-    call kmemcpy                                            ; copy partition table data to .data section in stage2
-    add sp, 0x6
 
-    mov ax, (FAT32_bpb_t_size + FAT32_ebpb_t_size)          ; len
+    ; copy bpb & ebpb to memory
-    push ax
+    __CDECL16_CALL_ARGS fat32_bpb, word [vbr_fat32_bpb_ptr], (FAT32_bpb_t_size + FAT32_ebpb_t_size) 
-    mov ax, word [vbr_fat32_bpb_ptr]                        ; src            
+    __CDECL16_CALL kmemcpy, 3
-    push ax
-    mov ax, fat32_bpb                                       ; dst
-    push ax
-    call kmemcpy                                            ; copy bpb & ebpb to memory
-    add sp, 0x6
 
     call SetTextMode
-    call disable_cursor
+    call disable_cursor_bios
-    print_string HelloPrompt_info
+
+    __CDECL16_CALL_ARGS HelloPrompt_info
+    __CDECL16_CALL PrintString, 1
+
+    ; setup the early heap
+    __CDECL16_CALL_ARGS early_heap_state
     
     ; enable A20 gate
     call EnableA20
-    print_string A20_Enabled_OK_info
+    __CDECL16_CALL_ARGS A20_Enabled_OK_info
+    __CDECL16_CALL PrintString, 1
 
     ; get system memory map
     call GetMemoryMap
-    print_string MemoryMap_OK_info
+    __CDECL16_CALL_ARGS MemoryMap_OK_info
+    __CDECL16_CALL PrintString, 1
 
-    ; enter unreal mode
+    ; enter unreal mode (enter PM w/ 16 bit code, 32 bit flat memory model & return to real)
+    ; ds, es will be set to the 64KiB STAGE2_SEGMENT, fs/gs will be flat/huge memory (4GiB)
+    ; use __REFLAT macros to re-flat ds/es for easy transfers to >1MiB
+    ; NOTE: if you modify a segment register you will need to re-unreal it
     call EnterUnrealMode
-    print_string UnrealMode_OK_info
+    __CDECL16_CALL_ARGS UnrealMode_OK_info
+    __CDECL16_CALL PrintString, 1
 
     ; FAT Driver setup
     call InitFATDriver
-    print_string InitFATSYS_OK_info
+    __CDECL16_CALL_ARGS InitFATSYS_OK_info
+    __CDECL16_CALL PrintString, 1
 
     ;
     ; Find first cluster of bootable file
     call SearchFATDIR
     push dword eax      ; save first cluster of bootable file
 
-    print_string FileFound_OK_info
+    __CDECL16_CALL_ARGS FileFound_OK_info
-    
+    __CDECL16_CALL PrintString, 1
+
     pop dword eax
     push dword eax      ; print Cluster of boot file
     call PrintDWORD     ; void PrintDWORD(uint32_t dword)
@@ -187,166 +188,103 @@ hcf:
 
 ; ##############################
 ;
-; SYSTEM CONFIGURATION FUNCTIONS
+; SYSTEM CONFIGURATION FUNCTIONS & MACROS
 ;
 ; ##############################
 
-; Prints a C-Style string (null terminated) using BIOS vga teletype call
+; set ds and es segments back to the base of the loader
-; void PrintString(char* buf)
+%ifnmacro __TINY_DS_ES
-ALIGN 4, db 0x90
+%macro __TINY_DS_ES 0
-PrintString:
+    mov ax, __STAGE2_SEGMENT
-    __CDECL16_ENTRY
+    mov ds, ax
-    mov di, [bp + 4]    ; first arg is char[] 
+    mov es, ax
-.str_len:
+%endmacro
-    xor cx, cx         ; ECX = 0
+%endif
-    not cx             ; ECX = -1 == 0xFFFF
-    xor ax, ax         ; search for al = 0x0
-
-    cld
-    repne scasb        ; deincrement cx while searching for al
-
-    not cx             ; the inverse of a neg number = abs(x) - 1
-    dec cx             ; CX contains the length of the string - nul byte at end
-.print:
-    mov si, [bp + 4]            ; source string
-.print_L0:
-    movzx ax, byte [si]
-    push ax
-    call PrintCharacter
-    add sp, 0x2
-
-    inc si
-    dec cx
-
-    jcxz PrintString.endp
-    jmp PrintString.print_L0    ; Fetch next character from string
-.endp:
-    __CDECL16_EXIT
-    ret                         ; Return from procedure
-
-; Prints a single character
-; void PrintCharacter(char c);
-ALIGN 4, db 0x90
-PrintCharacter:
-    __CDECL16_ENTRY
-.func:
-    movzx ax, byte [bp + 4]     ; AL = character c
-    mov ah, 0x0E                ; INT 0x10, AH=0x0E call
-    mov bx, 0x0007              ; BH = page no. BL =Text attribute 0x07 is lightgrey font on black background
-    int 0x10                    ; call video interrupt
-.endp:
-    __CDECL16_EXIT
-    ret
-
-; TODO: fix the prolog, epilog and stack usage to confirm with cdecl16
-; prints the hex representation of of val
-; void PrintDWORD(uint32_t val);
-ALIGN 4, db 0x90
-PrintDWORD:
-    __CDECL16_ENTRY
-.func: 
-    mov si, IntToHex_table
-    mov ebx, 16     ; base-16
-
-    mov eax, dword [bp + 4]     ;val
-
-    xor edx, edx
-    xor cx, cx
-.next_digit:
-    div ebx            ; dividend in edx:eax -> quotient in eax, remainder in edx
-    push dx            ; save remainder
-    inc cx
-
-    xor dx, dx
-    test eax, eax
-    jnz PrintDWORD.next_digit
-
-.zero_pad:
-    cmp cx, 0x0008
-    je PrintDWORD.print_stack
-    xor ax, ax
-    push ax
-    inc cx
-    jmp PrintDWORD.zero_pad
-
-.print_stack:
-    pop bx
-    dec cx
-    push cx
-
-    movzx ax, byte [bx+si+0]    ; bx = index into Hex lookup table
-    push ax
-    call PrintCharacter
-    add sp, 0x2
-
-    pop cx
-
-    jcxz PrintDWORD.endp
-    jmp PrintDWORD.print_stack
-
-.endp:
-    __CDECL16_EXIT
-    ret
-
-; ##############################
-;
-; SYSTEM CONFIGURATION FUNCTIONS
-;
-; ##############################
-ALIGN 4, db 0x90
-EnterUnrealMode:
-    __CDECL16_ENTRY
-.func:
-    cli                         ; no interrupts
-    push ds                     ; save real mode data/stack selectors
-    push es
-    push fs
-    push gs
-    push ss
-
-    push cs                               ; save real mode code selector
-    xor ax, ax                            ;
-    pop ax                                ; save cs to ax to setup far jump
-    mov word [__UNREAL_SEGMENT], ax    
 
+; for copying between locations in high memory
+%ifnmacro __REFLAT_DS_ES
+%macro __REFLAT_DS_ES 0
+    cli                                   ; no interrupts   
     lgdt [((__STAGE2_SEGMENT << 4) + unreal_gdt_info)]                 ; load unreal gdt
 
     mov eax, cr0                          
-    or al,1                               ; set pmode bit
+    or eax, 1                             ; set pmode bit
     mov cr0, eax                          ; switch to pmode
-    jmp short $+2
+    jmp short $+2                         ; i-cache flush
 
-    ;jmp far 0x0008:EnterUnrealMode.load_cs
+    mov ax, 0x10                          ; select descriptor 2
-    db 0xEA                               ; jmp far imm16:imm16
+    mov ds, ax
-    dw EnterUnrealMode.load_cs            ; error_far_ptr
+    mov es, ax               
-    dw 0x0008                             ; error_far_seg
+
-.load_cs:
+    mov eax, cr0
-    mov bx, 0x10                          ; select descriptor 2
+    and eax, ~1                           ; toggle bit 1 of cr0
-    mov ds, bx                            ; 10h = 0001_0000b
-                  
-    mov ss, bx
-    mov es, bx
-    mov fs, bx
-    mov gs, bx                            ; other data/stack to index 2 (off 0x10)
-    
-    and al,0xFE                           ; toggle bit 1 of cr0
     mov cr0, eax                          ; back to realmode
-    jmp short $+2
+    jmp short $+2                         ; i-cache flush
-    
-    ;jmp far 0x0008:EnterUnrealMode.unload_cs
-    db 0xEA                               ; jmp far imm16:imm16
-    dw EnterUnrealMode.unload_cs          ; error_far_ptr
-__UNREAL_SEGMENT:
-    dw 0x0000                             ; error_far_seg
-EnterUnrealMode.unload_cs:
-    pop ss
-    pop gs
-    pop fs
-    pop es
-    pop ds                                ; get back old segments
     sti
+
+%endmacro
+%endif
+
+; for copying from low memory to high memory (ds on a real segment, es in flat mode)
+%ifnmacro __REFLAT_ES
+%macro __REFLAT_ES 0
+    cli                                   ; no interrupts   
+    lgdt [((__STAGE2_SEGMENT << 4) + unreal_gdt_info)]                 ; load unreal gdt
+
+    mov eax, cr0                          
+    or eax, 1                             ; set pmode bit
+    mov cr0, eax                          ; switch to pmode
+    jmp short $+2                         ; i-cache flush
+
+    mov ax, 0x10                          ; select descriptor 2
+    mov es, ax                            
+
+    mov eax, cr0
+    and eax, ~1                           ; toggle bit 1 of cr0
+    mov cr0, eax                          ; back to realmode
+    jmp short $+2                         ; i-cache flush
+    sti
+
+%endmacro
+%endif
+
+ALIGN 4, db 0x90
+EnterUnrealMode:
+    __CDECL16_PROC_ENTRY
+    cli                                   ; no interrupts
+.func:    
+    lgdt [((__STAGE2_SEGMENT << 4) + unreal_gdt_info)]                 ; load unreal gdt
+
+    mov eax, cr0                          
+    or eax, 1                             ; set pmode bit
+    mov cr0, eax                          ; switch to pmode
+
+    ; set cs to a pm code segment (0x8) w/ the following
+    jmp 0x0008:EnterUnrealMode.set_segs
+.set_segs:
+    mov ax, 0x10                          ; select descriptor 2
+    mov ds, ax                            ; 10h = 0001_0000b
+    mov es, ax                            ; es to big data
+
+    mov fs, ax
+    mov gs, ax                            ; extra segments to big data as well
+.pm_start:
+    ; code here is running in protected mode w/ descriptor 0x8
+    ; insert any PM test code needed here
+.pm_end:
+    mov eax, cr0
+    and eax, ~1                           ; toggle bit 1 of cr0
+    mov cr0, eax                          ; back to realmode
+    jmp __STAGE2_SEGMENT:EnterUnrealMode.endp
 .endp:
-    __CDECL16_EXIT
+    sti                                   ; re-enable interupts
+
+    ; set ds, es to the STAGE2_SEGMENT, for our model (generally) ds == es == cs
+    ; fs, gs & ss are all still huge data model, and the macro(s) "__REFLAT_xxx" exists
+    ; to easily access data outside of 64KiB boundries using ds/es addressing
+    __TINY_DS_ES
+
+    __CDECL16_PROC_EXIT
     ret
 end_text:
 
@@ -423,14 +361,14 @@ unreal_gdt_start:
     ; entry 0 (null descriptor)
     dq 0                    ; first entry is null
 
-    ; entry 1 (16bit code 64KiB limit)
+    ; entry 1 (0x8) (16bit code 64KiB limit)
     dd 0x0000FFFF        ; Base Address(15:0) 31:16, Segment Limit(15:0) 15:0
     db 0x00              ; Base Address 23:16
     db 1001_1010b        ; Access Byte: Present, ring0, S = 1, executable (1), non-conforming, readable, Accessed
     db 0000_0000b        ; Flags: GR = 4KiB, attr = <DB/L/Avl>, Granularity = 4KiB & 16:19 of limit
     db 0x00              ; Base Address 31:24
 
-    ; entry 2 (16bit data segment with 4 GiB flat mapping)
+    ; entry 2 (0x10) (16bit data segment with 4 GiB flat mapping)
     dd 0x0000FFFF        ; Base Address(15:0) 31:16, Segment Limit(15:0) 15:0
     db 0x00              ; Base Address(23:16)
     db 1001_0010b        ; Access Byte: Present, ring0, S = 1, data (0), non-confirming, writable, present
@@ -529,6 +467,10 @@ fat32_state:
 align 16, resb 1
 SteviaInfo:
     resd 4
+
+align 16, resb 1
+early_heap_state:
+    resb ArenaStateStruc_t_size
 ;
 ; post-bss init globals
 ;

src/vbr/vbr.nasm

@@ -72,7 +72,7 @@ init:
     cld
     rep stosb                          
     
-    sub sp, 0x20                    ; local varible space
+    sub sp, 0x20                    ; local varible space (32 bytes)
     push bp
 
     sti                             ; all done with inital setup and relocation, reenable interupts